This invention relates to a method for the continuous manufacture of an undulating longitudinal material, and also to a device enabling this method to be carried out.
More precisely, the invention relates to the manufacture of such a material by transverse folding of a flexible longitudinal band such as a fibrous sheet, or a cloth composed of several fibrous sheets, or again a band of paper, fabric, non-wovens, or a sheet of glass, or again a strip of foam of plastics material etc.
At the present time use is made, for such a treatment, of an installation comprising basically a passage or corridor bounded by two rigid plane walls parallel to the general plane of the strip of material to be shaped, between which rollers situated close to one end of the passage project the strip to be treated, while retarding rollers situated close to the other end of the passage cause the bunching up of the strip inside this passage in the form of transverse folds.
Such an installation and such a procedure possess a certain number of considerable disadvantages.
A first disadvantage lies in the fact that it is not possible to treat in this manner strips or bands of rough-surfaced material, or strips coated with an adhesive or a binding agent, since such strips do not slide correctly along the walls of the passage, while they have a strong tendency to obstruct completely. The field of application of this known method is therefore limited, on the one hand by the nature of the materials which can be treated and, on the other hand, by the nature of the treatments between which the folding treatment is interposed.
In particular, as a result of the impossibility of adding a binding agent to the strip before the strip is folded, it is only possible to ensure that the folded material maintains its shape upon leaving the device by gluing it onto at least one support, which considerably limits the range of possible applications. Other disadvantages of this natural tendency of the material to re-adopt its original shape are also found, these disadvantages being due in this case to the fact that there exists, at a number of points in the known folding devices, possibilities of escape of the material, the consequence of which is a complete jamming of the device: this can occur notably at each of the ends of the passage, where there is a gap, oven though very small, between the walls of the passage and the projection rollers or retarding rollers for the strip; it is also the case between the various trains of retarding rollers.